Abstract
The nonuniformity in X-ray intensity distributions that occur due to an anode is referred to as “trend”. When trend exists, the true performance of a detector is not obtained, and the contrast-to-noise ratio（CNR）is decreased. In order to assess detector performance, a method to measure accurate CNR from the region of interest（ROI）is required. Therefore,we did development of a trend-removal method using quality control（QC）image of computed radiography（CR）mammography to decrease the influence of trend. Trend was removed in the ROI by segmentation of ROI data, without reduction of the ROI area specified by QC guidelines for CR mammography. The guideline ROI（400 mm2）were divided into square sub-ROIs with side lengths of 1/2, 1/4, 1/8, and 1/16（1.56 mm2）of the ROI. The CNRs were obtained by further averaging the mean pixel values and variances of each sub-ROI. Finally, the CNR of guideline ROI of 400 mm2,the trend-removal CNR of sub-ROI areas of 1.56 mm2, and trend-removal CNR of Legendre polynomials were compared using the Bonferroni statistical test. The difference of the two trend-removal CNRs was 0.13%, which not a statistical significant difference. Our trend-removal method was unaffected by ROI size.
